Various communication technologies in different spectrums and regions of spectrum continue to face obstacles. Given that radio spectrum is finite, the Federal Communications Commission (FCC) has in the past and continues to encourage the development and use of technology that makes efficient use of the radio spectrum. To this end, the FCC allocated a region of the radio spectrum from 220-222 MHz for, at least in part, the purpose of spurring the development and acceptance of new narrowband technologies. The 220-222 MHz range allocated by the FCC is divided up into 400 5 kHz-wide frequency ranges paired to provide 200 channels, such channels known as ultra-narrowband channels.
Some radio technologies implemented Amplitude Compandored Single Sideband (ACSB) signal processing systems/modulation to try and accommodate communication of data over these ultra-narrowband channels (5 KHz) within the 220-222 MHZ range, such as U.S. Pat. No. 5,222,250, titled SINGLE SIDEBAND RADIO SIGNAL PROCESSING SYSTEM, which issued Jun. 22, 1993. However, these radios were not widely used due to limited applications and the cost of dedicated hardware to enable these radios to operate via ultra-narrowbands and in the 220-222 MHz space. Typically, there was a need for specialty components and filters for each different band of intended use, limiting the application and practicality of this type of approach.
Traditional radios were able to transmit and receive radio signals across a short band. For example, the frequency span of a standard FM radio used to transmit or receive commercial FM music stations ranges from 88 Mhz to 109 Mhz. Frequencies outside this range could not be transmitted or received by frequencies that reside outside this identified spectrum making their use limited to that band. Additionally, traditional radios only support predetermined modulation schemes. In the example above, Frequency Modulation or FM was used to encode and decode the information over the radio waves.
In addition, other allocated frequency bands included stop bands in between usable bands of various sizes. Some technologies attempted to use these stop bands for communication, but due to the limited size of some of these stop bands, and the relative large amount of bandwidth required for various communications, some stop bands have yet to be effectively utilized.
Narrowband is currently defined as having an operational bandwidth of less than 6.25 Khz. Ultra-narrowband is currently defined as having bandwidth of less than 5 Khz. Typically, commercial usage has mostly been confined to the narrowband spectrums which the FCC has made prevalent in the land mobile radio and push to talk consumer radio spaces. While 6.25 Khz is common place, 5 Khz band requirements typically existed on only select bands such as the 220-222 Mhz spectrum. Ultra-narrowband was the FCC's attempt to conserve spectrum though the utilization of small bandwidths over identified spectrum. Requirements were not translated to other spectrum leaving the 220-222 Mhz spectrum as the only one requiring ultra-narrowband operation.
The FCC and other spectrum governing bodies might someday change regulations to increase the use of available spectrum. Changes such as these typically require slow implementation cycles where customers or often subjected to undue financial strain by having to, for example, repeatedly purchase new radios or equipment to be compliant with required changes.
As a result, improvements can be made to communication technology to better utilize available spectrum.